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-: Up until this point,

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we've learned how to read files,

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but we had this annoying thing

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with the cursor

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and then we had to close the file.

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So how can we fix this?

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Well, a better way to actually do something

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like this and do file io

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with Python is

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with the built in, with statement.

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Let me show you,

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instead of what we had before,

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what we're gonna say is,

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with open, the name of the file,

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and say as, whatever the variable you want.

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So my file, so now with open,

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you can actually do something like this,

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but you don't have to worry about closing.

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So, most of the time,

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you want to use the with statement,

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this is the proper way

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to work with files in Python.

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And if I save here

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and run my script,

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oh, I get an error,

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because I forgot the colon here.

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If I run again, there you go.

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I get my output,

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and I don't need to close my file.

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Everything is done for me.

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So this is a standard way to read a file.

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Now, what if we wanted to write to a file?

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So far we've only read,

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and actually, underneath the hood,

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open, has a default parameter,

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called mode, equals, two, R,

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which stands for read.

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So with mode R,

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we are able to read files.

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When we don't specify the mode,

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it automatically just assumes,

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we're reading.

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But if we wanted to write to a file,

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we can simply do W, for write.

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So if I run this,

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you see that I get an error now,

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unsupported operation, not readable,

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because, well,

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the file can only be written.

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So, in order for me to read and write,

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I can write r w, right?

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Well, let's see.

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Nope, that's actually not how it works.

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You would think it'll be rw,

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but this is a bit of a trick.

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In order to read and write,

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we do read plus,

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so that if I run this,

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all right, I'm reading and writing,

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and I get an empty list,

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because this is now empty.

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Okay, so let's write to a file here.

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Let's make this a little bit smaller,

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just so we can see, that's better.

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Let's say, that in this file,

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I wanna have text,

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and in this text,

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I am going to say my file dot write,

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and I can write whatever piece of text I want.

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So let's say, hey, it's me.

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So now in here,

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if I do print, text,

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and I run this, I get 11.

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Hmm, what is this 11?

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Well, this isn't really important right now.

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What we wanna focus on is,

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hey, it's me,

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I've written to a file.

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Okay, so let's say I wanted to open the file again,

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and actually write again.

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Let's say this time around,

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I'm going to write a smiley face.

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If I run this,

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and go back,

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alright, it looks like I wrote to the file,

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but, uh oh, is this what we wanted?

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When we write something to a file,

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the cursor resets.

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Remember, when we open a file,

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the cursor goes to zero

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and we write to the file,

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and, if there's something already existing in there,

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well, we override it.

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So we have to be careful,

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and by the way, this text file,

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just gave us, that we wrote two characters,

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the smiley face.

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Okay, so how can we fix this?

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How can we make sure

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that we don't break what we have previously,

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which is, hey, it's me,

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and I just wanna add a smiley face at the end.

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Well, we can use the append mode.

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The append mode, is a,

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and this appends to the end of the file.

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If I run this, look at that,

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hey, it's me, with a smiley face,

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it appends to the end.

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So, that's the append mode.

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Again, we can use W to write,

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and if I run this,

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it adds a smiley face.

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Now, why did it not do like last time,

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and overwrite the existing thing?

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Well, it's because of our mode.

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W allows us to write to a file.

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Previously, when we did read and write,

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what happened was,

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we read the file, let's run this again.

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Actually, let's go back to,

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hey, it's me, the way it was.

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And if I run this again,

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because we did read and write,

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the cursor was set to zero

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and overrode it,

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versus, if we just did the write,

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it will assume this is a new file,

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and we just wanna, well, just add the smiley face.

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If I click run here,

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you see that now is just smiley face.

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So you wanna be careful

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that you use the right mode,

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based on what you need.

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Now, let's say we wanted to create a file

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that doesn't exist.

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Let's have a file called, happy dot text.

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Or actually no, let's do sad.

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And this writes a sad face,

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but remember, we don't have this on our desktop.

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If I clear this,

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and look at our desktop,

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we don't have a sad dot text.

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If I do read plus here,

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so read and write,

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and I run this,

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I get a file not found error.

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If I do a write here,

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and I run this, right, it looks like it worked.

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If I look at the files, I have a sad text now.

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So now if I open it,

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I have it, sad face text.

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So write also, creates a new file,

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if it doesn't exist already,

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or overwrites the existing one.

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So you wanna be careful, once again,

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with the mode, if whether you wanna append,

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whether you wanna read,

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whether you wanna read and write.

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But, most of the time

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the most common ones are read, write, and append.

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Now, in the next video,

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I wanna talk about this idea of a file.

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I've written text files, for now,

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but we could have written anything.

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We could have done a dot py file,

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if I wanted to,

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but, what about accessing files

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that are in different locations,

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such as inside of folders?

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We're gonna explore that topic

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in the next video.